feat: add scoreboard with player names, per-category leaderboards, and themed tables

Add player_name column to games (migration included), with regex-based
validation and anti-abuse sanitization. New /scoreboard page shows recent
games from localStorage, popular categories with play counts, and top-10
per-category leaderboards sorted by completion time. Also includes
two-click reverse word matching, base URL prefix support for reverse-proxy
hosting, BasePageHandler refactoring, themed table CSS for all 5 themes,
and comprehensive test coverage for player names and scoreboard API.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

handlers/api.py

@@ -290,11 +290,19 @@ class GuessHandler(BaseAPIHandler):
         except (IndexError, KeyError, TypeError):
             return self._miss_response(game, session)
 
+        # Try forward and reversed letter order
+        reversed_letters = letters[::-1]
         word = (
             session.query(Word)
             .filter_by(game_id=game.id, text=letters, found=False)
             .first()
         )
+        if not word:
+            word = (
+                session.query(Word)
+                .filter_by(game_id=game.id, text=reversed_letters, found=False)
+                .first()
+            )
         if not word:
             return self._miss_response(game, session)
 
@@ -303,7 +311,7 @@ class GuessHandler(BaseAPIHandler):
             {"row": word.start_row + i * dr, "col": word.start_col + i * dc}
             for i in range(len(word.text))
         ]
-        if cells != expected_cells:
+        if cells != expected_cells and list(reversed(cells)) != expected_cells:
             return self._miss_response(game, session)
 
         return self._mark_found(session, game, word)